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Many challenges remain before we can fully understand the multifaceted role that natural organic matter (NOM) plays in soil and aquatic systems. These challenges remain despite the considerable progress that has been made in understanding NOM’s properties and reactivity using the latest analytical techniques. For nearly 4 decades, the International Humic Substances Society (IHSS, which is a non-profit scientific society) has distributed standard substances that adhere to strict isolation protocols and reference materials that are collected in bulk and originate from clearly defined sites. These NOM standard and reference samples offer relatively uniform materials for designing experiments and developing new analytical methods. The protocols for isolating NOM, and humic and fulvic acid fractions of NOM utilize well-established preparative scale column chromatography and reverse osmosis methods. These standard and reference NOM samples are used by the international scientific community to study NOM across a range of disciplines from engineered to natural systems, thereby seeding the transfer of knowledge across research fields. Recently, powerful new analytical techniques used to characterize NOM have revealed complexities in its composition that transcend the “microbial” vs. “terrestrial” precursor paradigm. To continue to advance NOM research in the Anthropocene epoch, a workshop was convened to identify potential new sites for NOM samples that would encompass a range of sources and precursor materials and would be relevant for studying NOM’s role in mediating environmental and biogeochemical processes. We anticipate that expanding the portfolio of IHSS reference and standard NOM samples available to the research community will enable this diverse group of scientists and engineers to better understand the role that NOM plays globally under the influence of anthropogenic mediated changes.

Background. Oncogenic rearrangements of the neuregulin 1 gene (NRG1) consist of a 5' partner fused to a 3' NRG1 sequence that retains the EGF-like domain, and are found in 0.2% of solid tumors including lung, breast and gastrointestinal (GI) cancers. Carcinomas of GI origin, including pancreatic and cholangiocarcinoma, represent around 20% of solid tumors harboring NRG1 fusions and there is no approved therapy for this group of cancers. The chimeric NRG1 oncoproteins bind to HER3/ERBB3 leading to trans-activation of other ERBB family members and trigger a signaling cascade that culminates in oncogenesis. Although targeting HER3 represents a rational therapeutic strategy for cancers harboring NRG1 fusions, this has remained relatively unexplored for NRG1 fusion-positive GI malignancies. In this study we investigated the efficacy of the anti-HER3 monoclonal antibody seribantumab in preclinical models of NRG1-driven GI cancers. Methods. We developed models of isogenic pancreatic cancer cells with NRG1 fusions by lentiviral-mediated cDNA expression of ATP1B1-NRG1 and SLC3A2-NRG1 fusions in immortalized pancreatic ductal cells (H6c7). Seribantumab efficacy was evaluated in isogenic cell lines and in patient-derived xenograft (PDX) models of pancreatic adenocarcinoma (CTG-0943, APP-NRG1 fusion) and intrahepatic cholangiocarcinoma (CH-07-0068, RBPMS-NRG1 fusion). Western blotting analysis was used to evaluate protein phosphorylation. Expression of NRG1 fusions was confirmed by RT-PCR and NGS. Results. Expression of NRG1 fusions in H6c7 cells resulted in enhanced phosphorylation of HER3 and AKT and increased sensitivity to afatinib, as compared to empty vector control cells (H6c7-EV). Treatment of H6c7-SLC3A2-NRG1 cells with seribantumab resulted in a dose-dependent inhibition of HER3 and AKT phosphorylation. Seribantumab treatment of H6c7-ATP1B1-NRG1 and H6c7-SLC3A2-NRG1 cells resulted in dose-dependent inhibition of cell growth with IC50 values of 0.05 and 0.2 µM, respectively. In contrast, growth of H6c7-EV cells was much less sensitive to seribantumab (IC50 > 1µM). Tumor growth inhibition was observed after administration of seribantumab to PDX mouse models of pancreatic adenocarcinoma and intrahepatic cholangiocarcinoma. While seribantumab (5 mg and 10 mg per dose, BIW) was equally effective to the clinical equivalent dose of afatinib (5 mg/kg QD) in the cholangiocarcinoma PDX model, the two doses of seribantumab were more effective than afatinib in the pancreatic cancer PDX model, causing tumor shrinkage of up to 55% (23-77% range). There was no shrinkage of afatinib-treated pancreatic PDX tumors. Our results here suggest that seribantumab is effective at reducing tumor growth in preclinical models of gastrointestinal cancers with NRG1 fusions. These data support the use of seribantumab to treat GI and other cancers with NRG1 fusions in the ongoing phase 2 CRESTONE study (NCT#04383210). Citation Format: Igor Odintsov, Allan J. Lui, Paul R. Bloom, Morana Vojnic, Shawn Leland, Marc Ladanyi, Romel Somwar. Preclinical activity of seribantumab in gastrointestinal cancers with NRG1 fusions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 935.

To study the structure and function of soil organic matter, soil scientists have performed alkali extractions for soil humic acid (HA) and fulvic acid (FA) fractions for more than 200 years. Over the last few decades aquatic scientists have used similar fractions of dissolved organic matter, extracted by resin adsorption followed by alkali desorption. Critics have claimed that alkali-extractable fractions are laboratory artifacts, hence unsuitable for studying natural organic matter structure and function in field conditions. In response, this review first addresses specific conceptual concerns about humic fractions. Then we discuss several case studies in which HA and FA were extracted from soils, waters, and organic materials to address meaningful problems across diverse research settings. Specifically, one case study demonstrated the importance of humic substances for understanding transport and bioavailability of persistent organic pollutants. An understanding of metal binding sites in FA and HA proved essential to accurately model metal ion behavior in soil and water. In landscape-based studies, pesticides were preferentially bound to HA, reducing their mobility. Compost maturity and acceptability of other organic waste for land application were well evaluated by properties of HA extracted from these materials. A young humic fraction helped understand N cycling in paddy rice (Oryza sativa L.) soils, leading to improved rice management. The HA and FA fractions accurately represent natural organic matter across multiple environments, source materials, and research objectives. Studying them can help resolve important scientific and practical issues.

Increased use of humic substances in agriculture has generated intense interest among producers, consumers, and regulators for an accurate and reliable method to quantify humic acid (HA) and fulvic acid (FA) in raw ores and products. Here we present a thoroughly validated method, the new standardized method for determination of HA and FA contents in raw humate ores and in solid and liquid products produced from them. The methods used for preparation of HA and FA were adapted according to the guidelines of the International Humic Substances Society involving alkaline extraction followed by acidification to separate HA from the fulvic fraction. This is followed by separation of FA from the fulvic fraction by adsorption on a nonionic macroporous acrylic ester resin at acid pH. It differs from previous methods in that it determines HA and FA concentrations gravimetrically on an ash-free basis. Critical steps in the method, e.g., initial test portion mass, test portion to extract volume ratio, extraction time, and acidification of alkaline extract, were optimized for maximum and consistent recovery of HA and FA. The method detection limits for HA and FA were 4.62 and 4.8 mg/L, respectively. The method quantitation limits for HA and FA were 14.7 and 15.3 mg/L, respectively.

Progress in determining nutrient availability in the rhizosphere is restricted by a lack of reliable and convenient methods for rhizosphere soil-water collection. A modified centrifugation method with a fluorocarbon (Fluorinert™,FC-70) as an immiscible displacement liquid was developed. Our objectives were to: i) obtain an adequate soil-water volume from a small rhizosphere sample within a reasonable time; ii) collect rhizosphere soil-water at container capacity (≈ 90% of field capacity) to determine soluble soil ions; and iii) evaluate FC-70 as an extractant. The soil used was a Beadle clay loam (fine, montmorillonitic mesic Typic Argiustoll) with low and high levels of CaCO3 (5 and 204g kg-1). Soil samples from the rhizosphere of 30-days-old sordan (sorghum (Sorghum bicolor L.), sudangrass (Sorghum sudanese L.) hybrid seedlings were thin-sectioned at 1-, 2- and 3-mm from the root surface. The extraction parameters (sample size, volume of extractant, relative centrifugal force and centrifugation time) were varied to determine optimal values. We obtained adequate amounts of aqueous solutions from moist soil (≈ 6 g) when mixed with 2 mL of FC-70, packed into a filter unit, and centrifuged for 1 hour at 14,500 × g. The displaced soil-water was analyzed by inductively coupled plasma spectrometry. The modified centrifugation technique with FC-70 offers a reliable, rapid, safe, and contamination-free method for obtaining unaltered soil-water from the rhizosphere, at a moisture content normally found in soil.

A rapid batch method was developed for the analysis of Si, Ca, Mg, and K in a large number of plant tissue samples by fusion with lithium metaborate (LiBO3) in graphite crucibles with the use of a molybdenum blue spectrophotometric analysis of silicon and FAAS for Ca, Mg, and K. Our method was tested for whole plant analysis of mature wild rice (Zizania palustris L.). Analysis of Si in plant tissue with LiBO3 in graphite crucibles is reliable and fast. Thirty-six samples can be ashed overnight, fused in one hour the next day, and analyzed for Si within approximately two hours.

Intensive cropping of Italian ryegrass (Lolium multiforum L.) in pots was used to assess the contribution of non-exchangeable K to plant uptake. The soils used were: two soils high in mica (illite) developed on recent alluvium plus two smectitic (beidellitic) soils and a soil of mixed mineralogy rich in mica. Four K treatments were used (0, 28.6, 143, and 286 mg kg-1 soil) with 8 successive monthly cuttings. A response of plant K uptake to added K was observed in all soils. Both 1.0 M NH40Ac and 0.2 M CaCl2 extractable K were depleted to a minimum level specific for each soil. The minima were lower in the old upland soils compared to the young alluvial soils. Uptake of K by Italian ryegrass induced K release from the non-exchangeable K to replenish the plant available pool of K ions. The release of mica interlayer K in the alluvial and in the high K smectitic soil supplied sufficient K to plants even under intensive cropping. The rate of mobilization of interlayer K was low in the smectitic soil with lower K. The lowest release rate was in the old high mica soil. Iron coatings may have inhibited mobilization of interlayer K. The rates of mobilization cannot be predicted from mineralogical and K-extraction data only. The rates of K uptake and the rates of K release by ryegrass under intensive cropping are potential values which can be used for modelling K availability to plants in the soils studied.

Objectives - The overall objective of this proposal was to explore the effects of soil properties and management practices on C sequestration in soils and off-site losses of N.The specific objectives were: 1. to investigate and to quantify the effects of soil properties on C transformations that follow OW decomposition, C losses by gaseous emission, and its sequestration by organic and mineral components of the soil; 2. to investigate and to quantify the effects of soil properties on organic N mineralization and transformations in soil, its losses by leaching and gaseous emission; 3. to investigate and to quantify the effects of management practices and plants root activity and decomposition on C and N transformations; and 4. to upgrade the models NCSOIL and NCSWAP to include inorganic C and root exudation dynamics. The last objective has not been fulfilled due to difficulties in experimentally quantification of the effects of soil inorganic component on root exudation dynamics. Objective 4 was modified to explore the ability of NCSOIL to simulate organic matter decomposition and N transformations in non- and calcareous soils. Background - Rates of decomposition of organic plant residues or organic manures in soil determine the amount of carbon (C), which is mineralized and released as CO₂ versus the amount of C that is retained in soil organic matter (SOM). Decomposition rates also greatly influence the amount of nitrogen (N) which becomes available for plant uptake, is leached from the soil or lost as gaseous emission, versus that which is retained in SOM. Microbial decomposition of residues in soil is strongly influenced by soil management as well as soil chemical and physical properties and also by plant roots via the processes of mineral N uptake, respiration, exudation and decay.

Aluminium is a pH-sensitive element that can cause acute toxicity symptoms in some organisms at aqueous activities of 10 µM or less1–3. Scientists working on agricultural systems have long been concerned with the deleterious effects of aluminium on crop roots4,5. More recently, environmental scientists have reported a potentially harmful biogeochemical link between acidic deposition onto forest soils and aluminium toxicity in forest and aquatic communities of northeastern North America and northern Europe6–8. Because of this general interest in aluminium toxicity as an environmental threat, there have been renewed efforts to model the chemistry and transport of aqueous aluminium in soils and surface waters. Here we propose that much of the spatial and temporal variability in aqueous aluminium chemistry can be accounted for by a two-component equilibrium model involving a solid-phase humic adsorbent and an aluminium trihydroxide mineral phase. Inputs for the model are solution pH, copper-extractable organic aluminium and the titratable carboxyl content of soil humus.

Honeylocust (Gleditsia triacanthos L.) seedlings were grown for 72 days in soil from a BC horizon of a Spodosol altered by adding four levels of AlCl3. Saturated paste extracts from controls to the highest AlCl3 treatment contained, respectively, 85 to 831 μM Al, 834 to 163 μM Ca and 316 to 35 μM Mg and had a pH of 4.4 to 4.0 Leaf, stem, and root concentrations of Al and P increased while those of Mg, Ca, and Zn decreased with increasing levels of Al. Growth decreased as Al, Al/Ca, and Al/Mg ratios in the extract increased. Growth was negatively related to tissue concentrations of Al, P, and Zn and positively related to tissue Mg and Ca. Growth was more closely correlated to elemental concentrations in the saturated paste extracts than in the SrCl2 extracts (1 part 0.01M SrCl2: 1 part moist soil).

The prehistoric Lowland Maya supported an elaborate civilization, which reached peak population densities in the tropical forests of Guatemala, Belize and southern Mexico during the Classic period between AD 300 and 900. It has been proposed that the Maya turned to labour-intensive construction of raised planting platforms in wetlands for year-round cultivation. Excavations at San Antonio Rio Hondo, northern Belize1, provided the first archaeological data for this hypothesis. In our analysis of data from the San Antonio site, we conclude that the only indisputable evidence that prehistoric wetland cultivation occurred comes from a time before peak population of the Classic period, and that the technique required less labour than previously envisioned. Exploitation of swampy terrain initially involved dry-season cropping without extensive ditching and later ditching, probably for soil drainage.

We found inconsistencies in the commonly used data for chlorophyll analysis in 80% acetone. Recently developed extinction coefficients for chlorophyll b in N,N-dimethylformamide (DMF) based on values from 80% acetone are low as a result of these inconsistencies. We determined extinction coefficients of chlorophyll a (Chl a) and chlorophyll b (Chl b) in DMF for wavelengths of 618 to 665 nanometers. The simultaneous equations necessary for quantifying Chl a, Chl b, or total Chl in DMF in the absence of other chlorophyllous pigments are: Chl a = 12.70A(664.5) - 2.79A(647); Chl b = 20.70 A(647) - 4.62A(664.5); total Chl = 17.90A(647) + 8.08A(664.5), where A = absorbance in 1.00 centimeter cuvettes and Chl = milligrams per liter.N,N-Dimethylformamide is a very convenient solvent for Chl extraction since it is effective on intact plant parts and Chl is quite stable in DMF. There was no difference in the amount of Chl extracted when plant tissue was stored for 1 or 3 days at three temperatures, with or without solvent added.

A collection of essays presenting original data that have allowed the author to reconstruct prehistoric Maya environment and subsistence.